This invention relates to antifoaming compositions having improved antifoaming properties, water dispersibility and stability.
Because of their superior antifoaming properties, silicone base antifoaming agents are used in a variety of industrial areas covering synthetic resins, synthetic rubber, oils and fats, fermentation, foods, fibers, petroleum, and medicines. Among others, antifoaming compositions for use under rigorous conditions including high temperatures, high pH and high shear forces are known from JP-B 52-19836, JP-B 52-22638, and JP-B 55-23084. For these compositions, further improvements in antifoaming properties were desired. To meet such demands, JP-B 3-14481, JP-B 3-14482, JP-A 63-147507, JP-A 1-317505 and JP-A 3-188905 propose compositions primarily comprising an organopolysiloxane having crosslinking units incorporated therein. These compositions, however, lack stability.
More recently, JP-A 5-271689, JP-A 8-196811 and JP-A 8-309104 propose oil compounds primarily comprising an organopolysiloxane having branched units incorporated in its structure. The antifoaming properties of these compounds are fairly improved, but not yet satisfactory.
An object of the invention is to provide an antifoaming composition having improved antifoaming properties, water dispersibility and stability.
The invention provides an antifoaming composition comprising (A) 58 to 90% by weight of an oil compound and (B) 10 to 42% by weight of a mixture. The oil compound (A) consists essentially of (i) 80 to 99.9% by weight of an organopolysiloxane and (ii) 0.1 to 20% by weight of finely divided silica. The organopolysiloxane (i) is composed of R13SiO1/2 units, R12SiO2/2 units and R1SiO3/2 units wherein R1 is independently a monovalent organic group of 1 to 20 carbon atoms, has a structure giving a compositional ratio of R13SiO1/2 units:R12SiO2/2 units:R1SiO2/3 units=(0.1 to 5):(90 to 99.8):(0.1 to 5) by mol %, and has a viscosity of 100 to 1,000,000 centipoise at 25xc2x0 C. The mixture (B) consists essentially of (iii) 30 to 99% by weight of a polyoxyalkylene-modified silicone oil of the following structural formula (1) and having a viscosity of 5,000 to 1,000,000 centipoise at 25xc2x0 C. and (iv) 1 to 70% by weight of a polyhydric alcohol alkyl ether having a molecular weight of 50 to 500. 
In formula (1), R2 is independently a monovalent organic group of 1 to 20 carbon atoms, A is a polyoxyalkylene-bearing group represented by xe2x80x94R3xe2x80x94O(CH2CH2O)p(CH2CH(CH3)O)qxe2x80x94R4 wherein R3 is a divalent hydrocarbon group of 1 to 4 carbon atoms, R4 is hydrogen or an alkyl, acyl or isocyanate group of 1 to 6 carbon atoms, p and q are numbers satisfying 10xe2x89xa6p+qxe2x89xa6100 and 10/90xe2x89xa6p/qxe2x89xa6100/0, the letters a and b are numbers satisfying 10xe2x89xa6a+bxe2x89xa61000 and 50/50xe2x89xa6a/bxe2x89xa699/1, and c is equal to 0 or 1.
A surfactant other than the polyoxyalkylene-modified silicone oil may be blended in the antifoaming composition in an amount of 0.1 to 50 parts by weight per 100 parts by weight of components (A) and (B) combined. This antifoaming composition can be dispersed in an aqueous dispersion of a water-soluble polymer.
The antifoaming composition of the invention exhibits improved antifoaming properties, good water dispersibility and high stability.
Briefly stated, the antifoaming composition of the invention contains (A) an oil compound and (B) a mixture as main components. The oil compound (A) is a main component for endowing the composition with antifoaming properties. The oil compound (A) consists essentially of (i) an organopolysiloxane and (ii) finely divided silica.
The organopolysiloxane (i) used herein consists essentially of the following structural units.
R13SiO1/2 R12SiO2/2 R1SiO3/2
Herein R1 is independently selected from substituted or unsubstituted monovalent organic (hydrocarbon) groups of 1 to 20 carbon atoms, for example, alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl; cycloalkyl groups such as cyclohexyl; alkenyl groups such as vinyl and allyl; aryl groups such as phenyl and tolyl; and substituted ones of these groups in which some or all of the hydrogen atoms attached to carbon atoms are replaced by halogen atoms, cyano groups, etc. such as chloromethyl, 3-chloropropyl, 3,3,3-trifluoropropyl, and cyanoethyl. It is recommended that methyl account for at least 90 mol % of the entire R1 groups.
Appropriate amounts of the R13SiO1/2, R12SiO2/2 and R1SiO3/2 units are combined to constitute the organopolysiloxane. If the quantity of R13SiO1/2 units is less than 0.1 mol %, the organopolysiloxane has a too high viscosity to handle. If the quantity of R13SiO1/2 units exceeds 5 mol %, the organo-polysiloxane has a too low viscosity to reduce foaming. If the quantity of R12SiO2/2 units is less than 90 mol %, the organopolysiloxane has a too low viscosity to reduce foaming. If the quantity of R12SiO2/2 units exceeds 99.8 mol %, the organopolysiloxane has a too high viscosity to handle. If the quantity of R1SiO3/2 units is less than 0.1 mol %, antifoaming properties become poor. If the quantity of R1SiO3/2 units exceeds 5 mol %, the organopolysiloxane has a too high viscosity to handle. For this reason, these units are contained to give a compositional ratio of R13SiO1/2 units:R12SiO2/2 units:R1SiO3/2 units =(0.1 to 5):(90 to 99.8):(0.1 to 5), and preferably (1 to 3):(94 to 98):(1 to 3) as expressed in mol %.
A lower viscosity is desirable from the standpoints of ease of dispersion and working of the organopolysiloxane, while a higher viscosity is desirable from the standpoint of foam suppression. With a viscosity of less than 100 centipoise, the resulting composition becomes less antifoaming. With a viscosity in excess of 1,000,000 centipoise, it becomes difficult to work the organopoly-siloxane into an emulsion. Then the organopolysiloxane should have a viscosity of 100 to 1,000,000 centipoise at 25xc2x0 C. and preferably 1,000 to 100,000 centipoise at 25xc2x0 C.
Finely divided silica (ii) used herein may be any well-known silica including wet silica and dry silica. Examples of silica powder include precipitated silica, silica xerogel, and fumed silica, which may be further surface treated to be hydrophobic. They are commercially available under the trade name of Aerosil from Nippon Aerosil K.K., Nipsil from Nippon Silica K.K., Cabosil from Cabonet, and Santocel from Monsanto Industrial Chemicals Co. Since better antifoaming properties are achieved with silica having a greater specific surface area, silica should preferably have a specific surface area of at least 100 m2/g, and more preferably at least 200 m2/g, as measured by the BET method.
If the amount of finely divided silica blended is less than 0.1% by weight of the oil compound (A), foam suppression becomes poor. If the amount of silica is more than 20% by weight, the oil compound has a too high viscosity to handle. For this reason, the amount of finely divided silica blended is 0.1% to 20% by weight, and preferably 1% to 10% by weight based on the oil compound (A).
The oil compound (A) can be prepared by mixing predetermined amounts of the organopolysiloxane and silica powder in a mixer having an appropriate agitating mechanism, heat treating the mixture at 60 to 200xc2x0 C. while mixing, and optionally, distilling off low-boiling fractions. Inorganic ammonium salts, organosilicon compounds and siloxane resins may be added, if desired, for the purpose of improving the retention of antifoaming ability, high-temperature performance, and dilution stability (see JP-B 4-42043, JP-A 5-261206 and JP-A 5-261207).
In the antifoaming composition of the invention, the mixture (B) consisting essentially of (iii) a polyoxyalkylene-modified silicone oil and (iv) a polyhydric alcohol alkyl ether helps emulsify and disperse the oil compound (A) in an aqueous medium.
Component (iii) is a polyoxyalkylene-modified silicone oil represented by the following formula (1). 
Herein R2 is independently selected from substituted or unsubstituted monovalent organic (hydrocarbon) groups of 1 to 20 carbon atoms, for example, alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl; cycloalkyl groups such as cyclohexyl; alkenyl groups such as vinyl and allyl; aryl groups such as phenyl and tolyl; and substituted ones of these groups in which some or all of the hydrogen atoms attached to carbon atoms are replaced by halogen atoms, cyano groups, etc. such as chloromethyl, 3-chloropropyl, 3,3,3-trifluoropropyl, and cyanoethyl. It is recommended that methyl account for at least 90 mol % of the entire R2 groups.
A is a polyoxyalkylene-bearing group represented by the following formula.
xe2x80x94R3xe2x80x94O(CH2CH2O)p(CH2CH(CH3)O)qxe2x80x94R4
Herein R3 is a divalent hydrocarbon group of 1 to 4 carbon atoms, for example, alkylene groups such as methylene, ethylene, propylene and butylene. R4 is hydrogen or a monovalent organic group of 1 to 6 carbon atoms selected from alkyl groups such as methyl, ethyl, propyl, butyl, pentyl and hexyl, acyl group such as acetyl, propionyl, butyryl, and hexanoyl, and isocyanate groups. If the sum of p+q is less than 10, the antifoaming composition becomes difficult to emulsify and disperse. If the sum of p+q is more than 100, a high viscosity leads to inefficient working. The letters p and q are numbers satisfying 10xe2x89xa6p+qxe2x89xa6100 and preferably 20xe2x89xa6p+qxe2x89xa670. If the value of p/q is less than 10/90, it becomes difficult to emulsify and disperse the oil compound (A). This requires 10/90xe2x89xa6p/qxe2x89xa6100/0, and preferably 20/80xe2x89xa6p/qxe2x89xa680/20.
If the sum of a+b is less than 10, the silicone oil has a too low viscosity and the resulting antifoaming composition becomes readily separable and thus unstable. If the sum of a+b is more than 1,000, the silicon oil has a too high viscosity and the resulting antifoaming composition becomes difficult to disperse in water, losing workability. Thus a and b should satisfy 10xe2x89xa6a+bxe2x89xa61000, and preferably 50xe2x89xa6a+bxe2x89xa6500. If the value of a/b is less than 50/50 or greater than 99/1, the antifoaming composition becomes difficult to emulsify and disperse. This requires 50/50xe2x89xa6a/bxe2x89xa699/1, and preferably 80/20xe2x89xa6a/bxe2x89xa695/5. The letter c is equal to 0 or 1.
Preferably, the polyoxyalkylene-modified silicone oil is liquid at room temperature. If its viscosity at 25xc2x0 C. is less than 5,000 centipoise, the resulting antifoaming composition becomes readily separable and thus unstable. If its viscosity is greater than 1,000,000 centipoise, the resulting antifoaming composition becomes difficult to disperse in water, losing workability. Thus the polyoxyalkylene-modified silicone oil has a viscosity of 5,000 to 1,000,000 centipoise at 25xc2x0 C. and preferably 10,000 to 500,000 centipoise at 25xc2x0 C.
It is preferred that component (iii) be dissolved in an aqueous solution of a surfactant in order to increase the dispersibility of the antifoaming composition in a foaming aqueous solution.
Component (iii) can be readily prepared by conventional well-known methods, for example, by effecting addition reaction of a polyoxyalkylene compound having an unsaturated group such as vinyl or allyl at an end of its molecular chain to an organopolysiloxane having a xe2x89xa1Sixe2x80x94H group in the presence of a platinum catalyst.
Component (iv) is a polyhydric alcohol alkyl ether which serves as an emulsifying aid. By blending component (iv), the mixture (B) is given an adequate fluidity so that the antifoaming composition is improved in uniformity. For this reason, component (iv) is used in admixture with component (iii).
The polyhydric alcohol alkyl ether may be of any desired structure as long as it has a (R5O) group within its molecule wherein R5 is an ethylene or propylene group. It may be straight or branched as shown by the following formula. 
Herein, R6 is independently hydrogen or a monovalent organic group of 1 to 6 carbon atoms, letters r, s and t are integers. Illustrative groups represented by R6 are hydrogen atoms and alkyl groups such as methyl, ethyl, butyl, pentyl and hexyl.
A polyhydric alcohol alkyl ether with a molecular weight of less than 50 has a low viscosity so that the antifoaming composition becomes unstable with the lapse of time. A molecular weight of more than 500 leads to a high viscosity and renders dispersion and working difficult. Therefore, the molecular weight is limited to the range of 50 to 500 and preferably 70 to 300.
If the amount of component (iii) is less than 30% by weight of the mixture (B), the antifoaming composition becomes less dispersible in water. If the amount of component (iii) is more than 99% by weight, the antifoaming composition becomes less uniform. For this reason, the amount of component (iii) is limited to 30% to 99% by weight and preferably 50% to 90% by weight of the mixture (B), with the reminder being component (iv).
The mixture (B) can be prepared by mixing components (iii) and (iv). In one preferred method, during synthesis of component (iii) from reactants, for example, synthesis of component (iii) from reactants by addition reaction, component (iv) is added to and admixed with the reactants. Then the mixture (B) is obtained in one step.
If the amount of component (A) is less than 58% by weight of the antifoaming composition, the composition becomes less effective to suppress foaming. If the amount of component (A) is more than 90% by weight, the composition becomes less dispersible in water and difficult to handle. Then the amount of component (A) should be 58% to 90% by weight and preferably 60% to 85% by weight of the composition. If the amount of component (B) is less than 10% by weight of the antifoaming composition, the composition becomes less dispersible in water. If the amount of component (B) is more than 42% by weight, the composition becomes less effective to suppress foaming. Then the amount of component (B) should be 10% to 42% by weight and preferably 15% to 40% by weight of the composition.
In order to further improve the dispersibility in water of the antifoaming composition comprising components (A) and (B), at least one surfactant other than component (iii) is preferably added as component (C). Any well-known surfactants may be used as component (C). Examples include sorbitan fatty acid esters, glycerin fatty acid esters, polyglycerin fatty acid esters, propylene glycol fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkyl ethers, polyoxypropylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyoxyethylene propylene glycol fatty acid esters, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, polyoxyethylene phytostanol ether, polyoxyethylene phytosterol ether, polyoxyethylene cholesterol ether, polyoxyethylene cholesteryl ether, alkanol amides, saccharide ethers, and saccharide amides. Water dispersibility is further improved by using at least one first surfactant having a HLB value of 1 to 10, preferably 2 to 8 in admixture with at least one second surfactant having a HLB value of 10 to 20, preferably 12 to 18. The first and second surfactants are preferably admixed in a weight ratio of from 1:9 to 9:1, more preferably from 2:8 to 8:2, and most preferably from 3:7 to 7:3.
If the amount of component (C) blended is less than 0.1 part by weight per 100 parts by weight of components (A) and (B) combined, the effect of improving water dispersibility is not fully exerted. If the amount of component (C) blended is more than 50 part by weight, it can adversely affect foam suppression. Thus the amount of component (C) blended is 0.1 to 50 parts, preferably 1 to 10 parts by weight per 100 parts by weight of components (A) and (B) combined.
The antifoaming composition of the invention can be prepared by mixing predetermined amounts of components (A) and (B) and optionally, component (C). Using a mixer such as a homomixer, Universal Mixer(trademark), Ultra Mixer(trademark), Planetary Mixer(trademark) or Combimix(trademark), these components are mixed until uniform. The mixing method is not critical. For example, the components are mixed while heating at a temperature of 40 to 150xc2x0 C.
In one preferred embodiment, an antifoaming composition obtained by blending components (A), (B) and optionally (C) is dispersed in an aqueous dispersion of a water-soluble polymer. The resulting aqueous antifoaming composition also falls within the scope of the invention. The aqueous antifoaming composition ensures easy operation when it is added to a foaming liquid.
The water-soluble polymer used herein may be selected from conventional well-known water-soluble polymers, for example, xanthane gum, starch, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose salts, polyvinyl alcohol, cellulose glycol salts, alginic salts, poly(meth)acrylic salts, long-chain alkyl-modified poly(meth)acrylic salts, and guar gum.
If the amount of the water-soluble polymer added is less than 0.01% by weight of the aqueous antifoaming composition, the composition becomes less stable. If the amount of the water-soluble polymer added is more than 10% by weight, the composition may have a too high viscosity and become less efficient to work with. Thus an appropriate amount of the water-soluble polymer added is 0.01% to 10% by weight and preferably 0.1% to 2% by weight based on the finally obtained aqueous antifoaming composition.
One preferred method for dispersing the antifoaming composition having components (A), (B) and optional (C) blended therein in an aqueous dispersion of a water-soluble polymer involves first mixing predetermined amounts of components (A), (B) and (C) as described above, adding a water-soluble polymer dispersion to the mixture, and mixing the resulting mixture in such a mixer as a homomixer until uniform. The mixing method is not critical. For example, the ingredients are mixed while heating at a temperature of 40 to 150xc2x0 C.